Integrated semiconductor optical device, method and apparatus for manufacturing such a device

ABSTRACT

The invention relates to an integrated semiconductor optical device comprising: a) an optical element ( 2 ), b) a housing ( 3 ) around said optical element ( 2 ), c) a glass window ( 51, 52 ) in said housing ( 3 ) allowing a light beam ( 71, 72 ) to pass through. In order to integrate the optics and the semiconductor optical device, while avoiding a difficult alignment procedure when using discrete lenses, the integrated semiconductor optical device according to the present invention further comprises a lens ( 61, 62 ) associated with said glass window ( 51, 52 ), said lens ( 61, 62 ) being directly replicated on the surface of said glass window ( 51, 52 ) outside said housing ( 3 ) by means of a replication method comprising the steps of: 1) filling a gap between the glass window and a mould with a liquid light-transmissive polymeric material, 2) curing the polymeric material to obtain said lens, and 3) removing the mould.

The invention relates to an integrated semiconductor optical devicecomprising an optical element, a housing around said optical element anda glass window in said housing allowing a light beam to pass through.The invention also relates to a method of manufacturing an integratedsemiconductor optical device as well as to a corresponding apparatus formanufacturing such a device.

In a semiconductor optical amplifier (SOA), light from a fibre must becoupled into the amplifier for its amplification. It must then becoupled into a fibre again. Usually, discrete standard lenses orcustomized lenses are used for this coupling. Such lenses are relativelylarge, and the alignment procedure is difficult and laborious.

It is therefore an object of the present invention to provide asemiconductor optical device as well as a method and an apparatus formanufacturing such a device, which can be integrated and by which theproblems described above can be avoided.

According to the present invention, this object is achieved by anintegrated semiconductor optical device as defined in claim 1 which, inaddition to the optical element, the housing and the glass window asmentioned above, further comprises a lens associated with said glasswindow, said lens being directly replicated on the surface of said glasswindow outside said housing by means of a replication method comprisingthe steps of:

-   -   filling a gap between the glass window and a mould with a liquid        light-transmissive polymeric material,    -   curing the polymeric material to obtain said lens, and    -   removing the mould.

A method of manufacturing such a device comprises the steps of:

-   -   embedding a semiconductor optical element within a housing        around said semiconductor optical element, said housing        comprising a glass window allowing a light beam to pass through,        and    -   directly replicating a lens on the surface of said glass window        outside said housing by means of a replication method as        mentioned above.

A corresponding apparatus for manufacturing an integrated semiconductoroptical device is defined in claim 4.

The invention is based on the idea of using the replication technologywhich is a well-known technology for manufacturing high-performance,diffraction-limited lenses. Such a replication method is particularlydescribed in U.S. Pat. No. 4,615,847 the disclosure of which is hereinincorporated by reference. Both spheres and flat substrates, usuallymade of glass, are used as base components, on which a thin layer, inthe tens of microns range, of polymer, i.e. the “replica”, is applied.Often, flat substrates are preferred because of costs and convenience.

According to the invention, said replication method is used to replicatea lens on the outer surface of a glass window which is part of thehousing. Thus, the flat glass window is used as a substrate for thereplication method. By integrating the lens and the semiconductoroptical device, the laborious alignment procedure of a discrete lens isnot required anymore, and the total device becomes very small andrelatively inexpensive.

In a preferred embodiment, the optical element is an optical amplifyingcrystal, the integrated semiconductor optical device is a semiconductoroptical amplifier and the housing comprises an input glass window and anoutput glass window, on each of which a lens is replicated. However, theinvention can be applied to any other semiconductor optical devicehaving one or more glass windows and requiring one or more lenses forcoupling in/out a light beam. Such fields of application comprisesemiconductor lasers where the laser chip is mounted inside the housing,telecom systems, optical networks, optical amplifiers, tunablelaserdiode transmitters, and high-power pump lasers.

The invention will now be explained in more detail with reference to thedrawing which shows an embodiment of an integrated semiconductor opticalamplifier according to the present invention.

Said semiconductor optical amplifier 1 comprises an amplifying crystal2, such as an Erlium Doped Fiber Amplifier (EDFA) or a Linear OpticalAmplifier (LOA), a housing 3 surrounding said crystal 2 and electricalconnections 4. The housing 3 comprises an input glass window 51 allowingan incoming light beam 71 from an input fibre 81 to pass through to theamplifying crystal 2 and an output glass window 52 allowing an amplifiedlight beam 72 to pass through for coupling into an output fibre 82.

Instead of using discrete lenses between the input fibre 81 and theglass window 51 or between the output glass window 52 and the outputfibre 82, respectively, coupling lenses 61, 62 are directly replicatedon the outer surface of the associated glass window 51, 52 using areplication method. The flat surface of the glass windows 51, 52 thusserves during manufacture as the substrate on which a mould is placed insuch a way that a gap remains between the mould and the glass window.Said gap is filled with a liquid light-transmissive polymeric material,such as a lacquer, which is hardened to obtain the lens. Finally themould is removed. Details of said replication method as well as detailsof an apparatus for implementing said replication method are describedin U.S. Pat. No. 4,615,847 which is herein incorporated by reference.

By using the invention, the optical coupling elements, i.e. the lenses,as well as the semiconductor optical amplifier itself can be integrated,which results in a small and inexpensive device. Furthermore, thealignment procedure of discrete lenses is avoided.

It should be noted that the invention is not limited to a semiconductoroptical amplifier as shown in the Figure, but can be applied to anyother semiconductor optical device where the housing comprises at leastone glass window allowing a light beam to pass through, such as a laserdiode.

1. An integrated semiconductor optical device comprising: an opticalelement (2), a housing (3) around said optical element (2), glass window(51, 52) in said housing (3) allowing a light beam (71, 72) to passthrough, and a lens (61, 62) associated with said glass window (51, 52),said lens (61, 62) being directly replicated on the surface of saidglass window (51, 52) outside said housing (3) by means of a replicationmethod comprising the steps of: filling a gap between the glass windowand a mould with a liquid light-transmissive polymeric material, curingthe polymeric material to obtain said lens, and removing the mould. 2.An integrated semiconductor optical device as claimed in claim 1,wherein said optical element (2) is an optical amplifying crystal,wherein said integrated semiconductor optical device is a semiconductoroptical amplifier and wherein said housing (3) comprises an input glasswindow (51) and an output glass window (52), on each of which a lens(61, 62) is replicated.
 3. A method of manufacturing an integratedsemiconductor optical device, the method comprising the steps of:embedding an optical element (2) within a housing (3) around saidsemiconductor optical element (2), said housing (3) comprising a glasswindow (51, 52) allowing a light beam (71, 72) to pass through, anddirectly replicating a lens (61, 62) on the surface of said glass window(51, 52) outside said housing (3) by means of a replication methodcomprising the steps of: filling a gap between the glass window and amould with a liquid light-transmissive polymeric material, curing thepolymeric material to obtain said lens, and removing the mould.
 4. Anapparatus for manufacturing an integrated semiconductor optical device,the apparatus comprising: means for embedding an optical element (2)beam within a housing (3) around said semiconductor optical element (2),said housing (3) comprising a glass window (51, 52) allowing a lightbeam to pass through, and means for directly replicating a lens (61, 62)on the surface of said glass window (51, 52) outside said housing (3) bymeans of a replication method, said means comprising: means for fillinga gap between the glass window and a mould with a liquidlight-transmissive polymeric material, means for curing the polymericmaterial to obtain said lens, and means for removing the mould.